1. Field of the Invention
The present invention concerns reduction of the perception of ammonia odor in ammonia containing compositions such as hair bleaches and colorants.
2. Discussion of the Related Art
Many hair treatment compositions contain ammonia and are characterized by an offensive odor.
For example, hair-bleaching agents based on a peroxide oxidation agent, such as hydrogen peroxide, urea peroxide, melamine perhydrate, etc. are generally used for the bleaching of human hair. The action of aqueous hydrogen peroxide solution per se, even under alkaline conditions, is too slow, so that hair damage may occur. Aqueous ammonia is an effective activator for the hair bleaching action of aqueous peroxide solutions, accelerating the oxidative destruction of the particles of the hair pigment (melanosomes), speeding up the rate at which the hair pigments are oxidized. It has therefore been customary to use ammonia in bleaching compositions for this purpose.
In addition, the pH of the aqueous hydrogen peroxide solutions must be adjusted to the alkaline side if they are to serve as effective bleaching agents for hair. Although the pH effect is different from the activator effect of ammonia (since the pH effect can be accomplished with alkaline materials other than ammonia), it has been common practice to use ammonia both for its activator effect and for its pH adjusting effect on the composition. As a consequence, with a few exceptions, essentially all the commercial hair bleaching compositions contain substantial quantities of ammonia.
Further, in hair dyes, the color vehicle for the dye intermediates is employed at a pH usually between about 9 and 11. Adjustment of pH to the desired level of alkalinity can be accomplished with ammonium hydroxide. The ammonium hydroxide base is preferred since ammonia assists in swelling the hair fiber and is easily removed.
Unfortunately, the presence or evolution of ammonia results in a particularly disagreeable strong ammonia odor. It is generally accepted that the unpleasant odor of ammonia cannot be masked even by perfuming.
Accordingly, efforts have been made in the prior art to provide ammonia-free hair bleaching compositions. One such attempt is described in U.S. Pat. No. 2,283,350. This patent describes the use of aliphatic amines or alkanolamines in place of ammonia or ammonium hydroxide to avoid the unpleasant ammonia odor. However, in this case, the resulting bleach mixture is more damaging (for the same degree of lightening) to the keratin hair fibers.
Another attempt at providing an ammonia-free hair bleach composition can be found in the U.S. Pat. No. 3,816,615 to Zeffern et al. In this case, activation of the peroxide oxidizing agent is accomplished by means of certain dicarbonyl compounds. In place of ammonium hydroxide, the patentees employ certain guanidine salts. This approach has not received any wide acceptance in the industry, which is probably due to the fact that the hair damage encountered in the use of the amines noted above is also encountered with the guanidine compounds.
Another approach to the odor problem has been to replace ammonia by odorless alkalinization agents such as alkali metal hydroxides, magnesium oxide or by alkanolamines, and to further accelerate the bleaching process in order to avoid the disadvantages of ammonia on the one hand and, on the other hand, to minimize the oxidative damage to the hair. U.S. Pat. No. 4,226,852 (Tesmann, et al.) teaches a two-component composition for bleaching hair comprising a peroxide oxidation agent, an ammonia-free alkalinization agent, and a guanidine derivative as bleaching accelerator. Unfortunately, guanidine derivatives are associated with hair damage.
A water insoluble gel is generally used to keep the bleach mixture on the hair fibers and prevent it from running or creeping away from the hair shaft and to run down off the head. The use of water-insoluble surfactants (see U.S. Pat. No. 2,283,350 for the use of high molecular weight alcohols for this purpose), however, greatly affects the lightening ability of the bleach mixture. To overcome reduced bleaching activity, high levels of ammonia are required. In conventional gels, the ammonia contained in the hair dye compositions is quickly given off from the gels to the environment, causing an odor problem. A loss of ammonia in the hair dye composition also lessens the covering power of the dyes, especially on gray hair. The same is essentially true of compositions that employ water-insoluble thickening agents. These also require relatively high levels of ammonia to raise the activity of the bleach composition to a suitable level.
U.S. Pat. No. 4,507,278 (DeMarco, et al.) teaches that, by utilizing water-soluble surfactant thickening agents, it is possible to dispense with the need for using ammonia as an activator. In this case, a non-ammonia alkalizing agent, and preferably one which does not have the potentiality for hair damage, can be employed to give the composition its appropriate pH. However, when only water-soluble surfactant thickening agents are employed, the viscosity of the product when it is applied to the head is too low for satisfactory application of the bleach. On the other hand, when an effort was made to increase the viscosity by the addition of water-insoluble surfactant thickening agents, it was found that the effectiveness of the bleaching composition, i.e., the rate at which the bleaching action occurred, was reduced to an unacceptable level. It was discovered that if a small quantity of ammonia is present in the composition (no greater than 0.55% by weight based on the total weight of the composition measured as ammonium ion concentration) and the ratio of water-soluble to water-insoluble surfactant thickener was maintained in the range of from 1.8 to 7.0, a highly effective product is obtained having the requisite level of bleaching activity, a suitable viscosity in use for application of the bleach, and substantially no ammonia odor.
Nevertheless, most hair coloring products in general use continue to be comprised of aqueous solutions with up to about 8% ammonia. Ammonia odors emanating from the coloring composition are difficult to mask and can be offensive to the hair color user.
There is thus a need for a method for the suppression of the ammonia odor in an ammonia-containing hair colorant.
The general understanding in the art is that ammonia odors are too intense to be masked by a perfume composition.
The present invention began by undertaking an investigation which ran contrary to this conventional wisdom. After extensive testing, it was surprisingly found that the perception of reduced ammonia odor does not depend on the maskant material""s odor detection threshold or on the perceived inherent intensity of the maskant material. Rather, it was found that the perception of the ammonia odor can be lessened by use of maskant materials with a high air diffusion coefficient.
Perfumes containing at least 25% of materials satisfying the criteria of the invention can be expected to cover the perception of ammonia better than those which do not.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention.